Conventional keyswitches with lever mechanism (scissors type keyswitch) are extensively used in keyboard for notebook computer. FIG. 1 shows a conventional keyswitch with a keycap 10a, a first lever 11a, a second lever 12a and a base 13a, wherein the first lever 11a and the second lever 12a are cross to each other. The first lever 11a has a pivotal shaft 14a pivotally connected to a pivotal stage 16a on the base 13a and the second lever 12a has a pivotal shaft 15a pivotally connected to a pivotal stage 17a on the base 13a, respectively. Each of the first lever 11a and the second lever 12 has a top end connected to a bottom face of the keycap 10a, whereby the first lever 11a and the second lever 12 form a lever mechanism.
The first lever 11a of the lever mechanism has a bump 18a placed at a lower center end thereof and the base 13a has a flange 19a on top face thereof and corresponding to the bump 18a. The bump 18a is in contact with and clamped by the flange 19a during downward stroke of the keycap 10a. 
A rubber dome (not shown) is placed between the keycap 10a and the base 13a. When the keycap 10a is guided by the lever mechanism for vertical up and down movement, the rubber dome below the keycap 10a will detach from or touch a flexible circuit board (not shown) on the base 13a and a switch on the flexible circuit board is turned off or on.
However, the conventional keyswitch for notebook computer has the problem of rotation and shaking. The keyswitches with lever mechanism have limitation of further improvement.